Floating shield in a triode sputtering apparatus protecting the base from the discharge



Dec. 1, 1970 R MO E 'O ETAL 3,544,445

Filed Sept. 1, 1966 FLOATING SHIELD IN A 'I'RIODE SPUTTERING APPARATUS PROTECTING THE BASE FROM THE DISCHARGE 4 Sheets-Sheet 1 I I I BY L/M/ A4 5/14/74 wa MM Dec. 1, 1970 os so ETAL 3,544,445

FLOATING SHIELD IN A TRIODE SPUTTERING APPARATUS PROTECTING THE BASE FROM THE DISCHARGE Filed Sept. 1, 1966 4 Sheets-Sheet 2 l l"" "'J$ I a 1 i 7 INVENTOR.

Dec. 1, 1970 R. M. MOSESON 'ETAL 3,544,445

FLOATING SHIELD IN A TRIODE SPUTTERING APPA RATUS PROTECTING THE BASE FROM THE DIS CHARGE 4 $heets-Sheet 3 Filed Sept. 1, 196g 3,544,445 ATUS 1970 R. M. MOSESON A!- FLOATING SHIELD IN A TRIODE SPUTTERING APPAR PROTECTING THE BASE FROM THE DISCHARGE 4 Sheets-Sheet 4.

Filed Sept. 1, 1966 United States Patent Wee 3,544,445 FLOATING SHIELD IN A TRIODE SPUTTERING APPARATUS PROTECTING THE BASE FROM THE DISCHARGE Roger M. Moseson, Rochester, and John H. Smith, Pittsford, N.Y., assignors, by mesne assignments, to The U.S. Cl. 204-298 8 Claims This is a continuation-in-part of abandoned application Ser. No. 516,472, filed Dec. 27, 1965.

The subject invention relates to the art of sputtering, and more particularly, to apparatus for depositing thin films of material on a surface of a substrate by sputtering.

The phenomenon referred to as sputtering has been known for many years. Initially, this phenomenon was considered undesirable, since it caused blackening of tube Walls, poisoning of cathodes and other deleterious effects in gas discharge and high vacuum apparatus and devices. More recently, sputtering has been developed to a highly sophisticated technique which permits the deposition of thin layers of material on various substrates. With the advent of miniaturization in electronics and related fields, sputtering techniques have become particularly valuable.

Advanced sputtering apparatus includes an enclosure and means for evacuating the enclosure and for establishing an ionizable atmosphere therein. The enclosure houses means for establishing an ion plasma the ions of which serve to sputter material from a suitably biased ion target. The substrate to be provided with a thin film is positioned in the enclosure so as to receive sputtered material from the ion target.

With advanced types of sputtering apparatus it has become the practice to provide means in the enclosure which are neither intended to participate directly in the generation of the ion plasma nor are supposed to sputter material onto the substrate. These means may, for example, be present in the form of a supporting structure or baseplate which is located in the enclosure to permit a proper positioning and support of the substrate. To name another example, these means may also be present in the form of a shield, between operative parts, or for an operative part, in the enclosure. To preclude fragility, many designers prefer to make these means of metal. The use of metals or possibly other electrically conducting materials is also indicated in an avoidance of an establishment of charge patterns over the surfaces of the means in question is of significance in a particular application.

The use of metal or other electrically conducting materials in the construction of the means in question has heretofore been believed to have the disadvantage of permitting these means to become a target for ions of energies sufficient to sputter material from these means. This undesirable eifect has in fact been noted in existing types of sputtering apparatus in which these means have customarily been connected to ground.

In connection with attempts to overcome the abovementioned undesirable effect, there have been suggestions to construct the means in question of the same material 3,544,445 Patented Dec. 1, 1970 as the ion target, so that the same material is sputtered from these means as from the target. While this solution appeared attractive, it was found to have severe drawbacks. In science and industry, the need for sputtering apparatus is steadily developing in the direction of apparatus which would be capable of sputtering various types of material, including abroad range of metals and even dielectric substances. Obviously each substitution of a target of one material for a target of another substance would call for a like replacement of the means in question, if the proposal just mentioned were adopted. In addition it is important in many applications that the deposition of the sputtered films be either uniform or deliberately nonuniform in a closely controlled fashion. The presence of one or more further ion targets constituted by the means in question, in addition to the principal ion target or targets, would interfere with the formation of highly uniform or deliberately non-uniform films.

The subject invention provides solutions, which do not entail these disadvantages, by providing means for establishing and maintaining a charge on the aforementioned electrically conducting means which repulses or diminishes the impingement of ions thereon. The electrical conducting means are disposed within a vacuum enclosure and could include such items as supporting structure for an ion target or anode. A baseplate located in the enclosure for supporting the support structure is another example. In any event, the electrical conducting means as used throughout this specification are those electrically conducting elements within the vacuum environment of a sputtering system which are in ion communication with the ion plasma and which have heretofore attracted ions by virtue of difierences in potential between ions in the plasma and the electrically conducting means. The repulsive charge at which the electrically conducting means are maintained is positive with respect to the cathode used in the sputtering apparatus of the instant invention and preferably on the order of the potential applied to the anode which complements the cathode.

In practicing the invention, the means in question are as before made of metal or other electrically conducting material. According to one aspect of the invention, these conducting means are maintained in an electrically floating condition to diminish the impingement of ions upon and undesirable sputtering of material from these conducting means. An electrically floating condition in the present sense exists if the means in question are essentially insulated from different conducting parts or structures of the sputtering apparatus, Without being connected to a source of electrical bias potential. In this electrically floating condition, the means in question are capable of accepting an electric charge without an immediate dissipation of such charge to parts or structures different from such means.

If the means in question are in an electrically floating condition, there will be a retention of the charges of ions which impinge onto these means in the operation of the apparatus. This retention can, of course, not be indefinite, inasmuch as some current conduction is present even in the best insulator. Also, if the floating means are positioned in the vicinity of a cathode, some electrons will be able to reach these means and neutralize the ion-imparted charge. On the other hand, a dissipation of the charge provided by impinging ions will be that slow, or impinging ions will reduce a potential imparted by impinging electrons to such an extent that subsequently arriving ions will impinge on the means in question in a progressively decelerated fashion. After a short period of time, ions willeither be incapable of reaching the means in question or will impinge with such low energies that no material which could objectionably contaminate sputtered films can 'be liberated from these means. Practical experiments have shown that the electrically floating means here under consideration assume during the operation of the sputtering apparatus a positive electrical potential which is in the vicinity of the positive potental of the anode of the sputtering apparatus. An apparatus in accordance with a preferred embodiment of the invention includes the above-mentioned enclosure, means for evacuating the enclosure and for establishing an ionizable atmosphere therein, and means for establishing an ion plasma in the enclosure. The apparatus further includes an ion target of material to be sputtered located in the enclosure to receive ions from the plasma. When the ion target is not mounted on the cathode as in prior art diode systems, means are used for electrically biasing the ion target to cause the impingement of ions from the plasma onto the target and the sputtering of material from the target. The substrate on which a thin film is tobe provided is located in the enclosure for the reception of material sputtered from the ion target. Electrically conducting means are located in the enclosure and present at least one surface to the plasma. As indicated above, these electrically conducting means may be present in the form of a supporting or baseplate structure or a shield between operative parts, or for an operative part, in the enclosure. According to the invention, the apparatus includes insulating means for maintaining the electrically conducting means just mentioned in an electrically floating condititon to diminish the impingement of ions upon and undesirable sputtering of material from these electrically conducting means.

From another aspect thereof, the subject invention provides also apparatus in which the above-mentioned conducting means are not maintained in an electrically floating condition, but have applied thereto an electrical potential. This expedient is particularly advantageousin, but is not limited to, apparatus in which the ion plasma is formed by a cathode and an anode and in which the electrically conducting means in question are, for instance, located in the vicinity of the cathode, such as in the form of a supporting structure or baseplate, for example, which may also serve asa bafl'le or shield. While such supporting structures or baseplates have heretofore customarily been connected to ground, the present aspect of the subject invention provides for the application of an electrical potential thereto which is on the order of the positive potential of the anode and thus positive with respect to the cathode. This reduces the energy of the impinging positive ions from the plasma onto the means in question and practically eliminates the objectionable sputtering of material from these means.

Another embodiment of the subject invention is directed to sputtering apparatus using metal or other electrically conductive bell jars or enclosures. A metal bell jar, just as other electrically conductive structures exposed to an ion plasma, can be sputtered. Because of its exposed state, a metal bell jar must be maintained electrically neutral in order to avoid hazardous working conditions for operating personnel. To avoid supttering of the metal bell jar while maintaining it electrically neutral, an electrically conductive shield is interposed between the ion plasma and the bell jar. The shield is electrically insulated from the base used in the sputtering apparatus. This shield is maintained either in an electrically floating condition or electrically biased such that ions from the ion plasma are repulsed resulting in a substantial reduction or elimination of its sputtering.

The subject invention and its various aspects will become more readily apparent from the following detailed description of a preferred embodiment and modifications thereof, illustrated by way of example in the accompanying drawing, in which:

FIG. 1 is an elevation, partially in section, of an apparatus according to the invention, with associated circuitry;

FIG. 2 shows a fraction of part of the apparatus of FIG. 1 and illustrates a modification in accordance with a further embodiment of the invention;

FIG. 3 shows a fraction of part of the apparatus of FIG. 1 and illustrates a modification in accordance with yet a further embodiment of the invention;

FIG. 4 is an elevation, partially in section, of another embodiment of the invention;

FIG. 5 shows a fraction of part of the apparatus of FIG. 4 and illustrates a modification; and

FIG. 6 shows a fraction of part of the apparatus of FIG. 4 and illustrates further embodiment of the invention.

The sputtering and film-depositing apparatus 10 shown in FIG. 1 comprises a base 11 having a central opening 12, and a removable bell jar 14 located on base 11 and sealed thereto at annular structure 15. A vacuum conduit 17 is connected to base 11 by a flange 18 and gasket 19. The space in base 11 and bell jar 14 is evacuated by means of a conventional high vacuum pump (not shown) which is connected to vacuum conduit 17 which is thus part of a means for evacuating the enclosure formed by the base 11 and bell jar 14.

The base 11 has a first lateral aperture 21 which communicates with the opening 12. A flange 22 is mounted to the base 11 at aperture 21 by a number of bolts 23. A sealing ring 25 seals the flange 22 to the base 11. A manually adjustable needle valve 26 is connected to flange 22 so that one of its ports communicates with the aperture 21. The other port of needle valve 26 is connected to a pipe 27 which leads to a gas tank 28. The gas tank, which may be a gas bottle, contains an ionizable gas, such as argon, which has theeffect of facilitating the ionization process in the bell jar 14, when admitted to the base 11 and jar 14 by the needle valve 26 in small quantities. It would also be possible to provide the necessary ionizing environment in bell jar 14 by adjusting the operation of the vacuum pump so as to permit a sufficient number of gas molecules to remain in the bell jar 14 during the evacuation process. However, the use of a separate gas tank and needle valve permits a more convenient and precise adjustment of the ionizing envlronment.

The base 11 has a second lateral aperture 31 which communicates with the space in bell jar 14 through substantially tubular filament shield 32. A flange is fastened to the base 11 at aperture 31 by a number of bolts 34. A sealing ring 36 seals the flange 33 to the base 11. Flange 33 has an extension 38 which forms the base of a cathode member 40. The cathode member further includes a filament 41 which is supported and supplied with electric current by a pair of leads 42 that extend through the flange 33 and are insulated therefrom by a pair of insulating sleeves 44. A pair of terminals 45 is mounted on sleeves 44 and connected to leads 42. In the illustrated embodiment the filament shield 32 carries a coil of tubing 47 which is connected to a supply of coolant liquid in a conventional manner not shown per se. The coolant liquid is caused to circulate through tubing or coil 47 so as to cool the filament shield. In this manner, overheating of the filament shield is avoided. A baflle plate or baseplate 50 encompasses the upper end of filament shield 32 and is supported by studs 51 and 52.

The baseplate 50 has a central aperture at which it is spaced and thus mechanically isolated and electrically insulated from the filament shield 32. The region of the base 11 at lateral aperture 31 serves as a means for maintaining the cathode shield in spaced relation from the baseplate 50. The studs 51 and 52 rest on and are supported by a pair of insulators 132 and 133. In this manner, the baseplate 50 is maintained in an electrically floating condition in that it will, at least for some time, retain an electric charge occurring thereon. If desired, the studs 51 and 52 may be made of insulating material, whereupon the insulators 132 and 133 can be dispensed with. If the insulators 132 and 133 are present and the studs 51 and 52 are of metal, the plate 50 is, of course, still in an electrically floating condition. The plate 50 and studs 51 and 52 are then jointly considered as an electrically conducting means which is insulated from any different part or structure of the apparatus. The operational significance of this electrically floating condition with respect to the illustrated embodiment will become apparent at this description proceeds.

The apparatus further includes a bushing 54 which extends through a bore 55 in flange 18 and is held therein by a nut 56. A tube 57 extends through and is sealed to the bushing 54. Tube 57 carries at its upper end an elbow member 59. A further tube 60 is connected to elbow member 59 to extend substantially perpendicularly to tube 57. An insulating wire 62 extends through tubes 57 and 60 and is connected to an anode support rod 64 which is supported by, but insulated from, the tube 60. The wire 62 is also connected to a terminal 65 which is mounted on the lower end of tube 57 by an insulator 66. An anode 68 is suspended from and electrically connected to support 64. Anode 68 has a substantially horizontal anode surface 70 which faces in the direction of filament shield 32.

After the base 11 and bell jar 14 have been evacuated, the filament 41 is supplied with a heating current from a battery 72 which is connected to the terminals 45. The anode 68 is positively biased with respect to the filament 41 by a battery 73. The negative terminal of battery 73 is connected to one of the filament terminals 45, and may be grounded or connected to the apparatus 10. The positive terminal of the battery 73 is connected to the anode terminal 65 through a conductor 74, a variable resistor 75, and a conductor 74'.

The heated filament 41 will release electrons to the anode surface 70. These electrons will collide with gas molecules present in bell jar 14. The gas molecules will thus be ionized and an ion plasma will form in the space between the anode and the plate 50. The ion plasma, which is schematically symbolized by a dotted outline 135, will extend substantially along an axis indicated by phantom line 77. The needle valve 26 may be adjusted from time to time to admit a desired number of gas molecules from the tank 28 to the ion plasma. Since the cathode is in the form of the heated filament 41, a large number of electrons will be released into the bell jar 14 and a vigorous formation of the ion plasma will take place.

A further bushing 80 extend through an aperture 81 in flange 18 and is held therein by a nut 82. A tube 84 extends through and is sealed to bushing 80. Tube 84 carries at its upper end an elbow member 85. A further tube 86 is connected to elbow member 85 to extend substantially perpendicularly to tube =84. An insulated wire '88 extends through tubes 84 and 86 and is connected to a target support 89 located adjacent and insulated from tube 86. The lower end of wire 88 is electrically connected to a terminal 90 which is insulated from tube '84 by an insulator 92.

An ion target in the form of a plate 94 is mounted on target support 89. The plate 94 is of the material to be sputtered and has a surface 95 disposed laterally of the ion plasma axis 77. In the illustrated embodiment, the surface 95 is not only spaced from axis 77 but also extends substantially parallel thereto. A substrate support 96 is mounted on and extends from the plate 50. The support 96 may at least in part be of an insulating material. For instance, a glass rod could be used as the stem 137 or an insulating plate as the foot 138 of the support. If the support 96 is of metal, the plate 50, this support 96 and, if the studs 51 and 52 are also of metal, these studs are jointly considered as electrically floating conducting means. Use of insulating material in the construction of the support 96 is, however, indicated if it should be found, in an apparatus built according to the subject invention, that the presence of an elongated conductor in the form of the support 96 would cause an excessive dissipation of electric charges from the plate 50 if electrically connected to the plate 50.

A substrate 98 is mounted on and suspend from the support 96. The substrate 98 has a surface 100 on which a thin film of material sputtered from target surface 95 is to be deposited. The surface 100 is disposed laterally of the plasma axis 77 so that it is spaced from axis 77 and faces the target surface 95 to receive material sputtered therefrom. In the illustrated embodiment, the substrate surface 100 extends substantially parallel to the target surface 95 and the anode surface 70 is spaced from and extends substantially at right angles to the surfaces 95 and 100.

The negative terminal of a battery 102 is connected to the target terminal through a variable resistor 103. The positive terminal of battery 102 is connected to the lead 74 which extends from the positive terminal of battery 73. The target 94 and surface are thus electrically biased so that ions from the ion plasma are caused to impinge on target surface 95. These impinging ions will sputter material from the target surface 95, which material will deposit itself on the substrate surface and form a thin film thereon. During operation of the illustrated apparatus, the anode current can be adjusted by means of resistor 75 and the target current by means of resistor 103.

The apparatus further includes a substantially cylindrical cover which rests on base '11 and is removable therefrom. The lateral wall of cover 110 may be of nonmagnetic wire mesh. A three-leg support 111 is placed on the top of cover 110. Three chains, two of which are apparent in the drawing at 112 and 114, are suspended from the support 111. A magnet structure 115 which houses an electromagnetic coil 17 is suspended from the latter chains by a number of further chains 116 which are connected to the former chains by hooks 118.

The coil 117 is energized by a battery 121 through a variable resistor 120, which permits adjustment of the current through coil 117 and thus of the magnetic field produced by this coil. The coil is of annular configuration and the magnetic field, which is diagrammatically indicated in the drawing by an arrow 123, extends in part along the axis 77. The chains 112, 114 and 116 and the hooks 118 permit the magnet coil to be raised, lowered and tilted with respect to the target 94 and substrate 98 to cause the formation of highly uniform or deliberately nonuniform films on the substrate surface 100.

In the illustrated embodiment, the plate 50 presents a. surface to the ion plasma symbolized by the dotted outline 135. During operation of the apparatus, ions will move from the plasma in the direction of the surface 140 and will impinge on this surface. These ions will tend to sputter material from the plate 50 that could contaminate the film forming on the substrate surface 100. Since the plate '50 is in accordance with the subject invention maintained in an electrically floating condition, impinging ions will build up a charge which will lessen and decelate further ion impingement to the point that no noticeable amount of material is anymore sputtered from the plate 50. An objectionable dissipation of material from the plate 50 to the substrate surface 100 is even avoided if electrons from the filament 41 should tend to charge the plate negatively. In that case, positive ions from the plasma will diminish such negative charge on the floating plate 50 and, as experiments have shown, will impart on the plate 50 a positive potential which will be in the vicinity of the potential at the anode 68. In operating apparatus of the type illustrated in FIG. 1, it has been found that the positive potential assumed by the floating plate 50 will only be from about to 20 volts less than the potential difference to produce objectionable sputtering of material from the plate 50. Even is some material should still be able to leave the plate, its energy will be that low that it cannot reach the substrate surface 100 to an objectionable extent. At the same time, the conductive nature of the plate 50 precludes the building up of any objectionable charges on localized surface areas of the plate.

In the illustrated embodiment, the plate 50 also serves as a baflle or shield with respect to the electrically conducting base structure, including base 11 and flange 18, of the apparatus. Owing to the arrangement of the plate 50 and the electrical charge assumed thereby, this base structure and also the filament shield 32 are guarded against ion impact.

In the illustrated embodiment, the filament shield 32 has an inner lining 142 of an insulating material, such as a ceramic. If desired, this lining may be provided by suitably tailored conventional high-temperature insulating tubes. The lining 142 reduces the impact of ions on the inside of the metallic portion of filament shield 32 and diminishes the emanation of contaminants from other causes from such inside. The functions of the lining 142 and of the electrically floating plate 50 thus jointly contribute to the formation of superior films on substrate surfaces.

FIG. 2 schematically illustrates fractions of the base plate 50, the stud 52, the tube 84 and the lead 88, all of which have been described above in connection with their associated parts. Theplate 50 is again maintained in an electrically insulated condition in the manner already described. The plateis, however, now positively biased by an electric source 150, here shown as a battery, which has its positive terminal connected to the plate 50 by a lead ,151 and its negative terminal connected to ground by a lead 152.

While the conductor 151 has been shown in a simple fashion, it will be understood that it may be led through a bushing (not shown) which extends through the flange 18 and is similar to the bushing arrangements 54 and 80 previously described.

The value of the positive potential imparted on the plate by the source 150 is made to be in the vicinity of the positive potential of the anode 68. In practical experiments, it has been determined that the plate 50 may be from about 10 to 20 volts negative to zero volts with respect to the potential at the anode 68, without objecionable sputtering occurring from the plate 50. The filament liner 142 and the other previously described parts and structures may again be employed under this modification.

FIG. 3 shows a further modification in which the de sired positive potential on the electrically insulated plate 50 is obtained by connecting this plate 50 to the previously mentioned conductor 74'. As illustrated, this connection takes place through a conductor 160, a resistor 161, which may be variable if desired, and a conductor 162. The conductor 162 may again be led through a bushing arrangement similar to the bushings '54 and 80 described and illustrated in connection with FIG. 1. It will be recalled in this connection that the conductor 74' is the conductor which is connected to the anode terminal 65 on the one hand and, through the conductor 74 and resistor 75, to the positive terminal of the anode battery 73 shown in FIG. 1.

The value of the resistor 161 shown in FIG. 3 is such that the plate 50 receives a positive potential that is similar to the positive potential of the anode. By way of example, the plate 50 may be up to about 10 to 20 volts lower than the positive potential existing at the anode 68 of the sputtering apparatus, without objectionable sputtering occurring from the plate 50. The filament liner 142 and the other parts and structures previously described in connection with FIG. 1 may again be employed under the modification illustrated in FIG. 3.

Another embodiment of the instant invention is shown in FIG. 4. Reference numeral 200 denotes the sputtering and film depositing apparatus of this embodiment. Metal bell jar 210 is disposed on base 11 either through a gasket (not shown) or directly. This bell jar is grounded in order to avoid electric hazard to operating personnel. Electrically conducting shield 214 is disposed within bell jar 210 to insulate the latter from impinging ions from ion plasma 135. Shield 214 is electrically insulated from base 11 through an annular insulating collar or standoff 215. As in the previously described embodiment, base 11 is grounded. In other respects the embodiment shown in FIG. 4 is identical with embodiment shown in FIG. 1 and hence will not be described in detail. The identical elements are referred to by identical reference numerals. The requirement for the inner shield 214 is dictated betated because it is undesirable to have an electrically charged structure exposed to operating personnel. The shield is maintained in the electrically floating state previously defined. The electrically floating state is achieved by the impingement of ions on shield 214 which creates a positive charge and the electrical insulation provided by the standolf 215 which prevents dissipation of the charge. This positive charge will eventually reach a steady state value approaching the potential of anode 68.

FIG. 5 illustrates an embodiment of the invention which is similar to FIG. 3 in that electrically conducting structure in ion communication with plasma is biased to inhibit or avoid impingement by positive ions. Thus base plate 50 is connected through lead 151 to the positive terminal of bias source 150. Shield 214 is connected through lead 216 to lead 151 and thus is biased positively with respect to the cathode in the same manner as base plate 50.

FIG. 6 is similar to FIG. 3 in that the electrically conductive structure facing ion plasma 135 is maintained at a positive potential With respect to the cathode through conductor 74. Thus base plate 50 and shield 214 are connected to conductor 74' through conductor 162, resistor 161 and conductor 16 0. For this purpose conductor 217 connects shield 214 to conductor 1'62. As before, resistor 161 is valued such that plate 50, and as a consequence shield 214, are maintained at a positive potential similar to the potential of anode 68.

In all of the illustrated embodiments, the insulating liner 142 may be extended upwardly as shown in FIG. 1 by dotted lines at 170, so as to augment the direction given to electrons traveling to the ion plasma in the vicinity of the ion target 94.

While specific examples have been described and illustrated, various modifications within the scope of the in vention will be apparent or suggest themselves to those skilled in the art.

What is claimed is:

1 An apparatus for depositing thin films by sputtering material from an ion target onto a substrate, which comprises:

an enclosure having a base;

means for evacuating said enclosure and for establishing an ionizable atmosphere therein;

a base plate having a central aperture, said base plate located above and electrically isolated from the base of said enclosure and defining a sputtering zone above and isolated from the base and isolated from the base of said enclosure;

means for establishing an ion plasma in said zone, said means incluindg an anode, a cathode, and a tubular cathode shield encompassing said cathode, with said shield extending through the central aperture and electrical isolated from said base plate;

means for positioning the ion target inside said zone;

means for applying an electrical bias to the ion target 9 to attract ions to the target and sputter material therefrom; and

means for positioning the substrate inside said zone for the reception of material sputtered from the ion target.

2. An apparatus as recited in claim 1 including a lining of insulating material in the tubular cathode shield and on the end thereof for diminishing undesired release of materials from the cathode shield.

3. An apparatus as recited in claim 1 including means for positively biasing said base plate.

4. An apparatus as recited in claim 2 including means for positively biasing said base plate.

5. An apparatus as recited in claim 1 including a second enclosure located within said first enclosure, said second enclosure electrically isolated from said first enclosure.

6. An apparatus as recited in claim 2 including a second enclosure located within said first enclosure, said second enclosure electrically isolated from said first enclosure.

7. An apparatus as recited in claim 3 including a second enclosure located within said first enclosure, said second enclosure electrically isolated from said first enclosure.

8. An apparatus as recited in claim 4 including a second enclosure located within said first enclosure, said second enclosure electrically isolated from said first enclosure.

References Cited UNITED STATES PATENTS 3,294,669 12/1966 Theuerer 204192 3,361,659 1/1968 Bertelsen 204192 3,410,775 11/1968 Vratny 204-192 3,133,874 5/1964 Morris 204298 3,296,115 1/1967 Laegreid et al 204192 3,305,473 2/ 1967 Moseson 204-298 3,341,442 9/1967 Kay 204-192 3,391,071 7/1968 Theuerer 204-192 ROBERT K. MIHALEK, Primary Examiner US. Cl. X.R. 204-492 

1. AN APPARATUS FOR DEPOSITING THIN FILMS BY SPUTTERING MATERIAL FROM AN ION TARGET ONTO A SUBSTRATE, WHICH COMPRISES: AN ENCLOSURE HAVING A BASE; MEANS FOR EVACUATING SAID ENCLOSURE AND FOR ESTABLISHING AN IONIZABLE ATMOSPHERE THEREIN; A BASE PLATE HAVING A CENTRAL APERTURE, SAID BASE PLATE LOCATED ABOVE AND ELECTRICALLY ISOLATED FROM THE BASE OF SAID ENCLOSURE AND DEFINING A SPUTTERING ZONE ABOVE AND ISOLATED FROM THE BASE AND ISOLATED FROM THE BASE OF SAID ENCLOSURE; MEANS FOR ESTABLISHING AN ION PLASMA IN SAID ZONE, SAID MEANS INCLUDING AN ANODE, A CATHODE, AND A TUBULAR CATHODE SHIELD ENCOMPASSING SAID CATHODE, WITH SAID SHIELD EXTENDING THROUGH THE CENTRAL APERTURE AND ELECTRICAL ISOLATED FROM SAID BASE PLATE; MEANS FOR POSITIONING THE ION TARGET INSIDE SAID ZONE; MEANS FOR APPLYING AN ELECTRICAL BIAS TO THE ION TARGET TO ATTRACT IONS TO THE TARGET AND SPUTTER MATERIAL THEREFROM; AND MEANS FOR POSITIONING THE SUBSTRATE INSIDE SAID ZONE FOR THE RECEPTION OF MATERIAL SPUTTERED FROM THE ION TARGET. 